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February 10, 2023
Separation Method of Tungsten and Molybdenum
Tungsten element is similar to molybdenum element in the fifth cycle. It belongs to refractory metal and has similar physical and chemical properties. Therefore, tungsten and molybdenum symbiosis phenomenon is more common in mineral resources. Tungsten can be used to manufacture tungsten chemical products such as tungsten powder and tungsten alloy, and can also be used to manufacture products such as filaments, knives, electronic products and medical instruments. Molybdenum can be used to make steel or make cast iron etc.
The separation method of tungsten and molybdenum is based on the slight difference between tungsten oxophilicity and molybdenum thiophilicity. At present, there are common separation methods such as precipitation method, solvent extraction method and ion exchange method. The following three main types are introduced:
1. Precipitation method
The main feature of the method is that the pH value of the solution after sulfidation is adjusted to 2.5-3.0 with an acid, and the molybdenum is formed into molybdenum trisulfide for precipitation and removal. But it is only applicable to molybdenum removal of sodium tungstate solution before transformation. In addition, the addition of a large amount of acid during the acidification process will also cause a large amount of neurotoxic gas hydrogen sulfide to escape. In addition, the presence of impurities such as phosphorus, arsenic, and silicon in the solution makes the acidic solution after molybdenum removal complicated, which has a significant impact on the subsequent transformation process.
2.Molybdenum sulfide and tungsten deposition method
The first step: before making artificial scheelite, the solution is vulcanized to transform molybdenum into molybdenum tetrasulfide which is not easy to precipitate. The second step: at the stage of synthesis of scheelite, molybdenum is inhibited with the solution to reduce the content of molybdenum in the product. Its production of tungsten trioxide products can be used in the manufacture of tungsten powder, tungsten carbide powder, catalyst for sulfur measurement, tungsten trioxide film, water pollution degradation photocatalyst, fuel cell carrier, resistance components and other products.
3. Quaternary ammonium salt solvent extraction method
With methyl trioctylammonium chloride as quaternary ammonium extractant, molybdenum and tungsten were separated in weakly alkaline solution with the separation coefficient of about 1100-5000, and the single stage molybdenum extraction rate was more than 90%. This method has higher molybdenum removal effect, higher purity of tungsten and improved operating environment to a certain extent, but it is difficult to extract.
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